Data from the world's languages illustrate that demonstratives grammaticalize as temporal auxiliaries/copulas, as focus markers, and as visual evidentials. However, these studies were done on the basis of individual languages or a specific grammaticalization path. In contrast, this paper argues that the various grammaticalization patterns of demonstratives reported in the world's languages are not totally isolated, but rather can be united by a single feature, distance: i.e., the spatial distance from the deictic center is conceptually transferred to temporal and evidential /epistemic (speaker's certainty associated with focus markers) domains. Moreover, since studies of this type of semantic extension are often concentrated on languages of Africa, the Americas, and Oceania, this paper adds cases from the Japonic languages to broaden the applicability of the proposed conceptual domain transfer, especially from space to epistemicity (focus). Specifically, this paper discusses the development of the cleft-like kakari musubi construction in Old Japanese and Old Okinawan, in which proximal, mesial, and distal demonstratives grammaticalized as focus markers are used in assertive, assertive/interrogative, and interrogative sentences respectively. It argues that such pathways represent a cognitively sound conceptual domain transfer from space to epistemicity and an embodied inverse relationship between spatial distance and epistemic certainty.